The present invention relates to an information processing apparatus which is low in power consumption and high in operability. More particularly, this invention relates to information processing apparatuses such as personal computers and word processors that are operated via keyboards and to information processing apparatus of a wide variety of application fields of a pen-base personal computer, a pen-base word processor, an electronic calculator, a portable electronic note book, a handy terminal device, a console of a plant, a kiosk such as a vending machine, an ATM (automated teller machine) and a street information service apparatus or a household furniture such as a table having a touch-sensitive display unit, etc.
In order to save an electric power of a primary battery, a secondary battery or a solar battery of an electronic apparatus such as a portable personal computer, a word processor or the like, an electric power saving control operation such as a resume operation for interrupting the supply of the whole power after information necessary for continuing work had been saved in a nonvolatile memory has heretofore been carried out when a user operation medium such as a keyboard or a mouse is not in use for a long period of time. Further, as a technique for preventing a battery from being consumed uselessly, JP-A-1-271796, for example, describes such a technique where a quantity of light of a back light that illuminates a display screen of a liquid crystal display device is adjusted in accordance with a quantity of external light. This previously-proposed method is effective, to a certain extent, for electronic equipments such as a portable personal computer, a word processor or a pen-based electronic equipment having a liquid crystal display panel with a back light in saving an electric power and also in improving viewability of picture screen. This method, however, has no consideration of the situation that the user operates these electronic equipments. There is then the problem that, when the user has left his seat and the electronic equipment has not been in use during a long period of time, the battery thereof is consumed uselessly.
Further, according to the above-mentioned conventional methods, in electronic apparatus having no user operation medium such as a keyboard or a mouse and operated with a pen or fingers, for example, the operation situation of these operation media cannot be utilized as a power saving control information.